A sheet feeding apparatus and an image forming apparatus, which can improve sheet feeding performance at low cost without degrading usability, are provided. Projections 42T and 43T are provided in abutting surfaces, which abut on lateral end of a sheet S, of a pair of lateral-end regulating portions 42 and 43 provided opposite each other. The projections regulates climbing over the lateral-end regulating portions of the sheet S when the sheet S is fed. Guide projections 100a and 100c are provided opposite each other along a cassette attaching direction in an inner wall surface of an attaching space, in which a sheet feeding cassette of an apparatus body is attached. When the sheet S climbs over the projections in feeding the sheet S, the sheet S is abutted on the guide projections to regulate upward movement of the sheet S.